Sensory processing sensitivity

Sensory processing sensitivity (SPS) is a temperamental or personality trait involving "an increased sensitivity of the central nervous system and a deeper cognitive processing of physical, social and emotional stimuli". The trait is characterized by "a tendency to 'pause to check' in novel situations, greater sensitivity to subtle stimuli, and the engagement of deeper cognitive processing strategies for employing coping actions, all of which is driven by heightened emotional reactivity, both positive and negative". A human with a particularly high measure of SPS is considered to have "hypersensitivity", or be a highly sensitive person (HSP). The terms SPS and HSP were coined in the mid-1990s by psychologists Elaine Aron and her husband Arthur Aron, who developed the Highly Sensitive Person Scale (HSPS) questionnaire by which SPS is measured. Other researchers have ap

Two-photon calcium imaging of neocortical projection neurons in whisker somatosensory cortex during goal-directed sensorimotor learning

Dimitra Angeliki Vavladeli

Abstract Excitatory projection neurons of the neocortex are thought to play important roles in per-ceptual and cognitive functions of the brain by directly connecting diverse cortical and subcortical areas. However, many aspects of the anatomical and functional organization of these inter-areal connections are unknown. The mouse primary somatosensory whisk-er barrel cortex (S1) serves as an important model for investigating the mammalian neo-cortex, and, here, I firstly investigate the structure and secondly the function of a specific subset of S1 cortico-cortical long-range projection neurons. In the first part of my thesis, I studied long-range axonal projections of excitatory layer 2/3 neurons with cell bodies located in S1. As a population, these neurons densely projected to secondary whisker somatosensory cortex (S2) and primary/secondary whisker motor cortex (M1/2), with additional axon in the dysgranular zone surrounding the barrel field, perirhinal temporal association cortex and striatum. The execution of a goal-directed behavior requires the brain to process incoming sensory information from the environment in a context-, learning- and motivation-dependent manner in order to perform specific motor actions. Cortico-cortical communica-tion in the context of goal-directed sensorimotor transformation has begun to be studied, but little is known about how signaling between interconnected cortical areas is modified by sensorimotor learning, as well as in response to changes in reward contingencies. Hence, in the second part of my thesis, I studied cortico-cortical dynamics in primary whisker somatosensory barrel cortex (S1) of mice during a combined whisker and audito-ry task. Using transgenic mice expressing GCaMP6f combined with two-photon micros-copy and retrograde labeling techniques, I chronically monitored the activity of excitatory layer 2/3 neurons in S1 projecting to M1 or S2, while mice learned the behavioral switch task. The results demonstrated that both classes of neurons responded after whisker and auditory stimulation. However, the whisker stimulus evoked response was stronger than the auditory stimulus evoked response. Neurons projecting to S2 exhibited stronger re-sponses compared to neurons projecting to M1 neurons. Those responses remained rela-tively stable across training sessions and under different reward conditions. Furthermore, both classes of neurons responded during spontaneous licking, but neurons projecting to S2 had larger licking-related responses compared to neurons projecting to M1. This work therefore furthers our knowledge of the structure and function of specific types of cortical projection neurons, which is a necessary step towards detailed under-standing of how sensory information might be signaled from primary sensory areas to downstream brain regions for further processing.

EPFL2018

Shedding light on excessive crying in babies

François Lazeyras, Dimitri Nestor Alice Van De Ville

Background Excessive and inconsolable crying behavior in otherwise healthy infants (a condition called infant colic (IC)) is very distressing to parents, may lead to maternal depression, and in extreme cases, may result in shaken baby syndrome. Despite the high prevalence of this condition (20% of healthy infants), the underlying neural mechanisms of IC are still unknown. Methods By employing the latest magnetic resonance imaging (MRI) techniques in newborns, we prospectively investigated whether newborns' early brain responses to a sensory stimulus (smell) is associated with a subsequent crying behavior. Results In our sample population of 21 healthy breastfed newborns, those who developed IC at 6 weeks exhibited brain activation and functional connectivity in primary and secondary olfactory brain areas that were distinct from those in babies that did not develop IC. Different activation in brain regions known to be involved in sensory integration was also observed in colicky babies. These responses measured shortly after birth were highly correlated with the mean crying time at 6 weeks of age. Conclusions Our results offer novel insights into IC pathophysiology by demonstrating that, shortly after birth, the central nervous system of babies developing IC has already greater reactivity to sensory stimuli than that of their noncolicky peers. Impact Shortly after birth, the central nervous system of colicky infants has a greater sensitivity to olfactory stimuli than that of their noncolicky peers. This early sensitivity explains as much as 48% of their subsequent crying behavior at 6 weeks of life. Brain activation patterns to olfactory stimuli in colicky infants include not only primary olfactory areas but also brain regions involved in pain processing, emotional valence attribution, and self-regulation. This study links earlier findings in fields as diverse as gastroenterology and behavioral psychology and has the potential of helping healthcare professionals to define strategies to advise families.

NATURE PUBLISHING GROUP2020

During capsaicin-induced central sensitization, brush allodynia is associated with baseline warmth sensitivity, whereas mechanical hyperalgesia is associated with painful mechanical sensibility, anxiety and somatization

Anne-Christine Schmid

Background Mechanical hyperalgesia and allodynia incidence varies considerably amongst neuropathic pain patients. This study explored whether sensory or psychological factors associate with mechanical hyperalgesia and brush allodynia in a human experimental model. Methods Sixty-six healthy volunteers (29 male) completed psychological questionnaires and participated in two quantitative sensory testing (QST) sessions. Warmth detection threshold (WDT), heat pain threshold (HPT) and suprathreshold mechanical pain (STMP) ratings were measured before exposure to a capsaicin-heat pain model (C-HP). After C-HP exposure, brush allodynia and STMP were measured in one session, whilst mechanical hyperalgesia was measured in another session. Results WDT and HPT measured in sessions separated by 1 month demonstrated significant but moderate levels of reliability (WDT: ICC = 0.5, 95%CI [0.28, 0.77]; HPT: ICC = 0.62, 95%CI [0.40, 0.77]). Brush allodynia associated with lower WDT (z = -3.06, p = 0.002; phi = 0.27). Those with allodynia showed greater hyperalgesia intensity (F = 7.044, p = 0.010, eta(2)(p) = 0.107) and area (F = 9.319, p = 0.004, eta(2)(p) = 0.163) than those without allodynia. No psychological self-report measures were significantly different between allodynic and nonallodynic groups. Intensity of hyperalgesia in response to lighter mechanical stimuli was associated with lower HPT, higher STMP ratings and higher Pain Sensitivity Questionnaire scores at baseline. Hyperalgesia to heavier probe stimuli associated with state anxiety and to a lesser extent somatic awareness. Hyperalgesic area associated with lower baseline HPT and higher STMP ratings. Hyperalgesic area was not correlated with allodynic area across individuals. Conclusions These findings support research in neuropathic pain patients and human experimental models that peripheral sensory input and individual sensibility are related to development of mechanical allodynia and hyperalgesia during central sensitization, whilst psychological factors play a lesser role. Significance We evaluated differential relationships of psychological and perceptual sensitivity to the development of capsaicin-induced mechanical allodynia and hyperalgesia. Fifty percent of healthy volunteers failed to develop mechanical allodynia. Baseline pain sensitivity was greater in those developing allodynia and was related to the magnitude and area of hyperalgesia. State psychological factors, whilst unrelated to allodynia, were related to mechanical hyperalgesia. This supports that the intensity of peripheral sensory input and individual sensibility are related to development of mechanical allodynia and hyperalgesia during central sensitization, whilst psychological factors play a lesser role.

WILEY2021